<!DOCTYPE html>
<html lang="zh-CN">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>简单的计时</title>
</head>

<body>
    <p>点击按钮，在等待 3 秒后弹出 "Hello"。</p>
    <button onclick="myFunction()">点我</button>
    <script>
        function myFunction() {
            setTimeout(function () { alert("Hello") }, 3000);
        }
    </script>
</body>

</html>